OSPF Areas: Normal, Stub, and NSSA
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Questions and Answers

Which OSPF area type receives all LSA types, including Type 1, 2, 3, 4, and 5?

  • Normal Area (correct)
  • Not-So-Stubby Area (NSSA)
  • All OSPF areas
  • Stub Area
  • Which OSPF area type is ideal for areas where external connectivity is limited?

  • Stub Area (correct)
  • Any OSPF area
  • Normal Area
  • Not-So-Stubby Area (NSSA)
  • What is a characteristic of Area Border Routers (ABRs) in Normal Areas?

  • They do not receive external routes.
  • They interface to other areas and can import/export routes. (correct)
  • They summarize external routes and inject a default route.
  • They receive only Type 1 LSAs.
  • What is a disadvantage of using Normal Areas?

    <p>They have higher memory and CPU usage due to larger routing and LSA databases.</p> Signup and view all the answers

    What is an advantage of using Stub Areas?

    <p>They have lower CPU and memory requirements.</p> Signup and view all the answers

    Which OSPF area type is typically used for core and main areas?

    <p>Normal Area</p> Signup and view all the answers

    What is a characteristic of Stub Areas?

    <p>They receive only Type 1, 2, and 3 LSAs.</p> Signup and view all the answers

    What is a disadvantage of using Stub Areas?

    <p>They may result in suboptimal routing due to limited external visibility.</p> Signup and view all the answers

    How do ABRs behave in Stub Areas?

    <p>They summarize external routes and inject a default route.</p> Signup and view all the answers

    What is a characteristic of Normal Areas in terms of routing information?

    <p>They have complete routing information, including external routes.</p> Signup and view all the answers

    What type of LSA is converted to Type 5 LSA by the ABR when advertised outside the NSSA?

    <p>Type 7 LSA</p> Signup and view all the answers

    Which type of OSPF area is suitable for core networks requiring full routing information, including external routes?

    <p>Normal Areas</p> Signup and view all the answers

    What is the main advantage of using NSSA over normal areas?

    <p>Increased flexibility in introducing external routes</p> Signup and view all the answers

    Which type of OSPF area is best suited for peripheral networks with limited external connectivity?

    <p>Stub Areas</p> Signup and view all the answers

    What is a disadvantage of using NSSA compared to stub areas?

    <p>Higher memory and CPU usage</p> Signup and view all the answers

    Which type of LSA is not received by an NSSA?

    <p>Type 5 LSA</p> Signup and view all the answers

    What is the primary function of an ABR in an NSSA?

    <p>Converting Type 7 LSAs to Type 5 LSAs</p> Signup and view all the answers

    What is a key trade-off in choosing between NSSA and normal areas?

    <p>Routing complexity versus resource constraints</p> Signup and view all the answers

    What is the primary advantage of using normal areas over NSSA?

    <p>Full routing information, including external routes</p> Signup and view all the answers

    Which type of OSPF area provides a compromise between stub and normal areas?

    <p>NSSA</p> Signup and view all the answers

    Study Notes

    OSPF Area Types

    • OSPF uses different area types to optimize routing and manage large-scale networks: Normal Areas, Stub Areas, and Not-So-Stubby Areas (NSSA).

    Normal Areas

    • Supports all OSPF route types, including intra-area, inter-area, and external routes (Type 5 LSAs).
    • Receives all LSA types (Type 1, 2, 3, 4, 5).
    • Interfaces with other areas and can import/export routes to/from other OSPF areas and external networks.
    • Typically used for core and main areas where full routing information is needed.
    • Pros: full visibility of the entire OSPF network, complete routing information for optimal path selection.
    • Cons: higher memory and CPU usage, more complex to manage.

    Stub Areas

    • Does not accept external routes (Type 5 LSAs), instead, a default route is injected by the ABR.
    • Receives only Type 1, 2, and 3 LSAs.
    • Summarize external routes and inject a default route into the stub area.
    • Ideal for areas where external connectivity is limited and a simple routing structure is required.
    • Pros: reduced LSA database size, lower CPU and memory requirements, simplified configuration and maintenance.
    • Cons: limited visibility of external networks, may result in suboptimal routing.

    Not-So-Stubby Areas (NSSA)

    • Allows limited external routes (Type 7 LSAs) that can be converted to Type 5 LSAs by the ABR.
    • Receives Type 1, 2, 3, and 7 LSAs, but not Type 5 LSAs.
    • Convert Type 7 LSAs to Type 5 LSAs for external areas.
    • Useful for areas that need to inject external routes without fully supporting all external LSAs.
    • Pros: flexibility to introduce external routes into a semi-stub area, reduced overhead compared to normal areas.
    • Cons: complexity in managing and converting Type 7 to Type 5 LSAs, may still have higher memory and CPU usage compared to stub areas.

    Choosing the Right OSPF Area

    • Depends on specific network requirements, including need for external routing information, resource constraints, and desired level of routing complexity.

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    Description

    This quiz compares and contrasts the three primary types of areas in OSPF: Normal Areas, Stub Areas, and Not-So-Stubby Areas (NSSA). Understand the characteristics and differences between them.

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